Gold casting method and apparatus

ABSTRACT

A method of making jewelry in which liquid gold is shaped into the desired hollow configuration using centrifugal/gyroscopic motion. The gold is liquidified either before application to a mold or melted after it is deposited into the mold. A centrifugal force is applied to the mold to press the gold against the interior walls of the mold and the gold is allowed to solidify. Once solid, in the preferred embodiment, the gold is “hardened” using a pulse of air pressure applied to the interior of the mold.

[0001] Priority for this application is claimed from U.S. Provisional Patent application Ser. No. 60/184,787, filed on Feb. 24, 2000, and entitled “Gold Casting Method and Apparatus”.

BACKGROUND OF THE INVENTION

[0002] This patent relates to the manufacture of jewelry and more particularly to the casting of gold jewelry.

[0003] Over the past few years, a variety of techniques have been attempted for the efficient manufacture of gold jewelry, including those described in U.S. Pat. No. 6,003,228, entitled “Method for Making a Decorative or Jewelry Item” issued on Dec. 21, 1999, to Riggio; U.S. Pat. No. 5,979,537, entitled “Wax Replica and Soluble Core Insert Used for Producing Hollow Jewelry Ring” issued on Nov. 9, 1999, to Baum; and U.S. Pat. No. 5,916,271, entitled “Hollow Jewelry Ring having Inner Round Design” issued on Jun. 29, 1999, to Baum, all of which are incorporated hereinto by reference.

[0004] Generally, there are several methods of producing a finished jewelry product from gold mill stock. The stock chosen depends on the method and the desired result. For Example flat stock is used where the piece is to be die struck. Wire is used where the metal is to be made into chain.

[0005] When a piece is to be cast in a mold, a quantity of gold in granulated form is melted and poured into the mold. The problem with this method is that if the piece is three dimensional, it comes out of the mold in a solid form making it extremely heavy and therefore expensive. It is very difficult to cast the piece with a hollow core.

[0006] One way to make the core hollow is to use a wax core and melt it out later. This is called “lost wax casting” The result is a piece that is still too heavy because the thick walls enclosing the hollow core.

[0007] Another method is to electroplate a heavy coating of gold onto a wax core. Sharp, crisp detail is not possible and the wall thickness is not consistent.

[0008] It is clear that a more efficient method and apparatus for casting gold will result in a better gold product.

SUMMARY OF THE INVENTION

[0009] Within the present invention, the principle of centrifugal force is employed. Granulated gold is heated to a liquid state and poured into a spinning mold. Centrifugal force throws the molten gold away from the center and deposits it onto the interior walls of the mold where it cools and solidifies.

[0010] This technique both eliminates the need for a core and also allows the molten gold to pick up any design which has been cut into the interior walls of the mold.

[0011] In one embodiment, to avoid handling very hot molten gold and the possibility of a dangerous spill, the mold becomes a small oven called a crucible. In this technique, the casting grains are dropped into the mold where they are heated to a molten state and spun. At this point what we have is a combination crucible and centrifuge.

[0012] Most centrifuges spin on a horizontal plane. To assure an even distribution of gold within the mold, should spinning the centrifuge along a horizontal plane along result in a casting which is too thick on the equatorial plane and too thin at the poles, the centrifuge is spun alternately in two directions, once horizontally and then vertically as the metal cools and solidifies.

[0013] In this context, to obtain the multiple plane spinning action, a powered yoke spins the crucible/centrifuge so that while the mold is spinning in one plane, the entire assembly is spinning 90 degrees opposite. This technique eliminates the problem of an uneven depositing of gold on the mold's interior walls.

[0014] Once the mold and centrifuge are established, experimentation quickly establishes the correct temperature and the proper amount of gold grains used to achieve the desired wall thickness and the length of time required to spin the crucible/centrifuge.

[0015] When the finished piece is removed from the two or four part mold it is ready for finishing.

[0016] The invention, together with various embodiments thereof will be more fully explained by the accompanying drawings and the following descriptions.

DRAWINGS IN BRIEF

[0017]FIGS. 1A, 1B, 1C, 1D, and 1E illustrate the preferred embodiment of the invention in which a two part die or mold is used.

[0018]FIG. 2 shows a four part mold which is employed as described above.

[0019]FIGS. 3A, 3B, and 3C illustrate a mold which is rotated around two axis.

[0020]FIGS. 4A, 4B, 4C, and 4D illustrate the steps taken to expand the solidified gold within the mold and create an article of jewelry.

[0021]FIGS. 5A and 5B illustrate two different techniques of applying a carbon layer within the mold to ease removal of the finished product.

[0022]FIG. 6 illustrates the step of placing solid gold granules within the mold and then melting these granules within a rotating oven.

[0023]FIG. 7 illustrates the embodiment in which melted gold is applied to the mold immediately prior to the application of centrifugal force to the mold.

DRAWINGS IN DETAIL

[0024]FIGS. 1A, 1B, 1C, 1D, and 1E illustrate the preferred embodiment of the invention in which a two part die or mold is used.

[0025] The two parts of the die, 10A and 10B, are secured to each other and molten gold 11 is poured into the top of the die (as seen in FIG. 1A). In this embodiment, mold 10 is subjected to a high revolutions-per-minute centrifuge 12 involving two planes of movement (horizontal and vertical). This creates movement through three dimensions. During a portion of the application of centrifugal forces, the mold or die 10 is heated 13 so that the gold does not harden before the die is rotated as shown in FIG. 1B.

[0026] The die 10 is removed (FIG. 1C) and die (10A and 10B) is opened, as illustrated by arrows 14A and 14B (FIG. 1D) to release the hollow gold item 15 formed.

[0027] As noted earlier, in one embodiment of the invention, to avoid handling very hot molten gold and the possibility of a dangerous spill, the mold becomes a small oven called a crucible. In this embodiment, the casting grains are dropped into the mold where they are heated to a molten state and spun.

[0028] Most centrifuges spin on a horizontal plane. If the resulting casting is too thick on the equatorial plane and too thin at the poles, the centrifuge is spun alternately in two directions, once horizontally and then vertically as the metal cools and solidifies.

[0029] Ideally the mold is spun in a “gyroscope” type of centrifuge so that the resulting gold layering within the mold has a substantially uniform thickness.

[0030]FIG. 1E illustrates that a pattern 16 on the interior edge of die 10 is naturally imparted into the gold item being made.

[0031]FIG. 2 shows a four part mold 20A, 20B, 20C and 20D which is employed as described above.

[0032] When the finished piece is removed from the two or four part mold, the gold product is ready for finishing, which often involves the application of a fastening mechanism to the gold item so that it can be worn by a wearer.

[0033]FIGS. 3A, 3B, and 3C illustrate a mold which is rotated around two axis.

[0034] The die/mold 30 is loaded as outlined above and then placed within a harness 31 as shown in FIG. 3A. Harness 31 allows the die/mold 30 to be rotated in two differenct directions 32A and 32B simultaneously (as illustrated in FIGS. 3B and 3C).

[0035] In the embodiment of FIG. 3C, most of the centrifugal force 32C is on the equatorial (horizontal) plane; this results in more metal being deposited on the sides of the mold 30.

[0036] If a yoke is also involved, as illustrated in the embodiment of FIGS. 3A and 3B, then as the yoke revolves 32B while the mold simultaneously spins 32A, then the centrifugal force distributes the melted gold substantially uniformly within mold 30. In this manner, a uniform thickness to the gold is assured.

[0037]FIGS. 4A, 4B, 4C, and 4D illustrate the steps taken to expand the solidified gold within the mold and create an article of jewelry.

[0038] Within the present discussion, gold, due to its high malleability, is used for description of the invention's technique. Those of ordinary skill in the art readily recognize that the present invention is also useful for other precious metals which are used as the “value” metal of jewelry and are also malleable. Using the technique described above, a tubing of gold is made within mold 20.

[0039] Hollow probe 41 is inserted into mold 40 as illustrated by arrows 42A. This insertion of probe 41 pierces into the core of the mold, which is hollow after the gold has been pressed against the interior walls of mold 40 and has cooled to a solid state.

[0040] Once probe 41 is properly positioned within mold 40 (as shown in FIG. 4B), the interior of the tube is pressurized to expand the tube to engage the walls of the mold. This expansion of the tube provides a “work hardening” of the gold. In practice, it has been found that 24 k gold, when work hardened in this manner, has a hardness comparable to traditional 14 k gold.

[0041] A further advantage obtained during the expansion of the tubing within the mold is that the wall thickness of the tubing is reduced, sometimes as much as 30%. The expanded tubing therefore uses much less gold for manufacture of an article of jewelry when compared with the same article of jewelry manufactured using traditional methods.

[0042] This decreased thickness though does not make the jewelry less durable as the gold has been hardened as outlined above.

[0043] As a final step, as shown in FIG. 4C, the probe is removed and the two halves of the is mold 40A and 40B are separated as illustrated by arrows 42B to release the gold component 43.

[0044] The final step in creating the article of jewelry is illustrated in FIG. 4D where gold component 43 has fasteners 44A and 44B secured thereto. In this illustration, an earring is created which uses fasteners 44A and 44B to secure the gold component 43 to a wearer.

[0045] Since the gold is now hardened, the use of an alloy is not required to obtain durability. Less gold is required since the wall thickness is reduced. The overall affect is the ability to produce an article of jewelry made of higher purity of gold for less cost.

[0046] The pressurization which is inflicted upon the gold tubing is accomplished using either water or air (other gasses can also be used). Air is the preferred medium for expansion of the gold.

[0047]FIGS. 5A and 5B illustrate two different techniques of applying a carbon layer within the mold to ease removal of the finished product.

[0048] As shown in FIG. 5A, the opening at the top of mold 50 is positioned below sprayer 51 which deposits a quantity of carbon 52 therein. The mold is then subjected to the centrifugal forces as outlined above to spread the carbon 52 throughout the interior of mold 50.

[0049] In an alternative, the sprayed carbon is applied to the opened mold which is then assembled ready for the application of the gold.

[0050] In some embodiments, as shown in FIG. 5B, mold 53A and 53B is opened to accept a pre-cast carbon shape 54 which is designed to fit the interior cavity of mold 53A and 53B. Pre-Cast carbon shape 54 is then enclosed within the mold as indicated by arrows 55.

[0051] While these figures illustrate two different methods of applying a carbon film within the mold, those of ordinary skill in the art readily recognize a variety of other methods which can be employed in this context.

[0052]FIG. 6 illustrates the step of placing solid gold granules within the mold and then melting these granules within a rotating oven.

[0053] Solid gold 61, dust or chunks in this illustration, are deposited into mold 60 as shown by arrows 62A. Once the prescribed amount of solid gold 61 has been placed within mold 60, mold 60 is secured within rotating oven 63 (stationary during the placement of mold 60) as shown by arrow 62B.

[0054] In one embodiment of the invention, intermixed with solid gold 61 are precious stones (diamonds, emeralds, etc.). These stones intermix with the gold as it melts and become bonded to the gold as it solidifies.

[0055] Once fully secured within oven 63, the assembly is rotated as described above using shaft 64. If a gyroscopic action is desired, a second motor within oven 63 rotates mold 60 therein.

[0056] In this manner, solid gold is deposited into the mold and is then melted and spun into shape. Thereafter, while still spinning, the mold's temperature is allowed to cool so that the shape of the gold within the mold is preserved.

[0057]FIG. 7 illustrates the embodiment in which melted gold is applied to the mold immediately prior to the application of centrifugal force to the mold.

[0058] In this embodiment, dispenser 71 is used to apply a quantity of liquid gold 72 into mold 70. Mold 70 is already heated to prevent the liquid gold 72 from solidifying until the proper shape has been established using yoke 73.

[0059] It is clear that the present invention provides a more efficient method and apparatus for casting gold. 

What is claimed is:
 1. A method of manufacturing a component of jewelry comprising the steps of: a) rotating a mold containing melted gold therein; b) while said mold is rotating, allowing said melted gold to solidify; and, c) expanding said solidified gold against the walls of said mold using compressed air passed into a core of said mold.
 2. The method according to claim 1 , further including the steps of, after said gold has solidified: a) allowing said mold to become stationary; and, b) creating an opening into the core of said mold for the passage of said compressed air.
 3. The method according to claim 2 , wherein the step of passing compressed air into the core of said mold includes the step of pulsing said air pressure into the core of said mold.
 4. The method according to claim 2 , wherein the step of rotating said mold includes the step of rotating said mold around an axis.
 5. The method according to claim 2 , wherein the step of rotating said mold includes the step of rotating said mold through three-dimensional space.
 6. The method according to claim 1 , further including the steps of: a) placing a carbon liner in said mold; and, a) pouring melted gold into the mold.
 7. The method according to claim 1 , further including, prior to the step of rotating a mold containing melted gold, the steps of: a) placing a carbon liner in said mold; b) placing solid gold within said mold; and, c) melting said solid gold within said mold.
 8. A method of manufacturing gold jewelry comprising the steps of: a) rotating a mold containing melted gold therein; b) while said mold is rotating, allowing said melted gold to solidify; and, c) removing the solidified gold from said mold.
 9. The method according to claim 8 , further including the steps of: a) after said gold has solidified, bringing said mold to a stationary position; and, a) expanding said solidified gold against the walls of said mold by, 1) creating an opening into a core of said mold, and, 2) pulsing compressed air into the core of said mold.
 10. The method according to claim 8 , wherein the step of rotating said mold includes the step of rotating said mold around a central axis.
 11. The method according to claim 8 , wherein the step of rotating said mold includes the step of rotating said mold through three-dimensional space.
 12. The method according to claim 8 , further including, prior to the step of rotating said mold, the steps of: a) placing a carbon liner in said mold; and, b) pouring melted gold into the mold.
 13. The method according to claim 8 , further including, prior to the step of rotating the mold, the steps of: a) placing a carbon liner in said mold; b) depositing solid gold within said mold; and, c) melting said solid gold within said mold.
 14. The method according to claim 8 , a) further including the step of placing said mold containing solid gold into an oven; and, b) wherein the steps of rotating said mold and melting said solid gold is done simultaneously while said mold is within said oven.
 15. The method according to claim 8 , further including the step of attaching a fastening mechanism to said solidified gold, said fastening mechanism adapted to secure said solidified gold to a wearer.
 16. A method of manufacturing jewelry comprising the steps of: a) rotating a mold containing melted gold therein; b) while said mold is rotating, allowing said melted gold to solidify; c) expanding said solidified gold against the walls of said mold using compressed air passed into a core of said mold; d) removing said solidified gold from said mold; and, e) securing to said solidified gold, a fastening mechanism adapted to secure said solidified gold to a wearer.
 17. The method according to claim 16 , prior to the step of rotating the mold, further including the step of pouring melted gold into the mold.
 18. The method according to claim 16 , further including, prior to the step of rotating the mold, the steps of: a) placing solid gold within said mold; and, b) melting said solid gold within said mold.
 19. The method according to claim 16 , wherein the step of expanding said mass of gold against the walls of said mold includes the step of pulsing said compressed air into the core of said mold.
 20. The method according to claim 16 , further including the steps of: a) removing said solidified gold from said mold; and, b) attaching to a fastening mechanism to said solidified gold, said fastening mechanism adapted to secure said solidified gold to a wearer. 